In recent years, a hybrid vehicle including both an internal combustion engine and an electric motor used as power sources has been developed for increasing fuel efficiency and reducing an amount of exhaust gas.
As in Patent Document 1, such a hybrid vehicle includes a clutch between drive wheels and an internal combustion engine, and the clutch is connected/disconnected to switch between a series mode and a parallel mode.
In the series mode in Patent Document 1, the clutch is disconnected to drive a power generator with power of the internal combustion engine, the electric motor coupled to a drive axle is driven by electric power obtained by the power generator to cause the vehicle to travel. In the parallel mode, the clutch is connected to drive the drive axle with power of the internal combustion engine and drive the electric motor coupled to the drive axle with electric power obtained by a storage battery to cause the vehicle to travel with both the power of the internal combustion engine and the power of the electric motor according to a driving state of the vehicle.